Unscrew all cabinet hardware with a screwdriver. Remove the hardware and screws and set them together out of the way.
Combine 1/3 cup trisodium phosphate with 1 gallon water in a bucket. Dip a scrub brush in the mixture and scrub down the cabinets, removing dirt and grease that gives them a dull appearance.
Pat the cabinets down with a clean old towel and allow them to air dry. Press a piece of 100-grit sandpaper on the bottom of the electric sander. Run the sander across the surface area of the cabinets. Repeat with 200-grit sandpaper and then 300-grit sandpaper. Finally, to bring the cabinets to an even greater shine, buff the cabinets with a sheet of 500-grit sandpaper.
Wipe down the cabinets with a tack cloth to remove the dust from sanding. Dip a 3-inch nylon brush into a coat of a high-gloss slightly tinted polyurethane finish. The gloss will give your cabinets a natural shine and the tint will restore any slight fading of color. Allow the polyurethane to dry overnight and then apply a second coat, giving it at least 24 hours to dry.